Adding a Pilothouse (second) Battery Bank

Hi All,
I’m starting to spend many nights aboard her now and am finding that after a full night the main battery bank gets pretty low and the voltage drops below 11.5 volts. The problem I am having is that my equipment in the pilothouse is a bit more sensitive to voltage and also does use a decent amount of power since I run things like an 8 camera NVR at all times, etc. While I know I could spend time figuring out what to turn off I thought it might make more sense and give me more flexibility to add a second battery bank. I dont have much time to get this designed before I leave north so hoping for some suggestions. Also I already researched the Autostart generator option and thanks to great feedback from this group decided that’s not the right way to address this.

My boat currently has an Xantrex 3012 that charges the main bank (6v batteries, 12v system). The power then goes to two panels, one in the main salon which controls all the house systems (plumbing, lights, etc). And then a second panel in the pilothouse which just does running lights and electronics. There are a set of large power (+/-) cables running up to the pilothouse for this but no room to add a second set of cables.

My question is:
Would I either be able to add a second battery bank in the pilothouse charged by the 3012, the complication I see is that I only have that one set of power cables running up to the pilothouse.
Or what about adding a totally separate bank, charged by a 40a charger powered off the 110v inverter power in the pilothouse which would allow for full charging under power and prioritize charging the electronics/critical batteries versus the house system. If I did the separate system I would put a selector switch so the pilothouse panel could be powered by either the house bank or upper bank. This could be handy should the bilge ever flood (hopefully never).

I know little to nothing about proper DC power system design and could use some pointers in the right direction.

Thanks!
Arthur

My first concern about putting batteries in the pilothouse would be the weight. Can the floors hold that much? Also what would that do to the stability and the COG of the boat?
Why not just add to your house bank?

I’m not too worried about the weight, but valid concern. The same deck is designed to hold a very heavy boston whaler dingy as well on 4 mounts, I checked and there is no difference in construction/reenforcement for the dinghy. And since I’m on a lighter RIB there is several hundred expected lbs I can add so stability shouldn’t be too much of a concern. Not to mention the boat is also designed to take another dinghy up top with modifications and I think one KK54 runs that way which would put much more weight even higher up. (On my boat the dinghy sits right in front of the pilothouse).
As far as adding to the main bank it would mean I couldn’t get down into the midships bilge which I just dont think is practical to have to remove batteries to work on any of the plumbing systems (or battery system for that matter). I had thought about adding taller/more expensive batteries but the prices get to the point I could easily pay for the second bank and it has added benefits if I can figure out how to do it well. Since the batteries and my main plumbing systems are in the same mid-bilge I do worry a throughhull hose failure could put me in a bad spot with zero power, since everything I need to run operates of the pilothouse panel an isolated bank would be useful, although hopefully it never comes to that.

FWIW, in the interest of time as you prep for your trip... I think I'd add batteries to the main bank (and/or go taller), charge more often with your genset (or maybe just run the thing most of the time), maybe go to a larger alternator if you haven't already, and turn some non-essential stuff off overnight (assuming you're not underway).

Then that'll give you time to ponder a maybe more elegant comprehensive solution... which could include larger chargers, solar, whatever.

Arthurc said:

Or what about adding a totally separate bank, charged by a 40a charger powered off the 110v inverter power in the pilothouse which would allow for full charging under power and prioritize charging the electronics/critical batteries versus the house system.

Click to expand...

Not sure I understand that. Using an inverter to charge batteries is using batteries to charge batteries... with some efficiency loss in between.

??

-Chris

The inverter to charge the batteries was just where I would get the AC power from, but it would be easy to make it so the charger would only charge when the main engine or Genset is on. I have a pretty good Maretron setup now with the relays, etc so writing in that control would be simple.
As far as alternators, etc, all of that is fine on the boat, oversized even, I think its a 200 and a 160 off the main engine, this is purely an issue of me greedily wanting to not worry about counting amps every night while leaving things like my full Nav and N2K network, and camera system running 24x7 since they do things like anchor watch. The tall batteries are an option but looks to be several thousand dollars based on what I looked at, more batteries arent really an option.
Also its not about solar as I generally kill my Genset about sun down, its purely a question of added capacity for the night.

The tall batteries might be the simplist but does mean in the case of water in the bilge I am out of luck. Although I haven’t actually tested operating the boat with the battery switch off.... (I have a separate starting system)

AC

Generally, you are going to be better off using one large battery bank than multiple smaller battery banks.


DC->AC->DC is a huge waste of power. I wouldn't consider that.


I think you are frankly better off turning off stuff you don't need running 24/7. Either that, or run your genset overnight. Either of those would be a better soluntion, IMO, to adding a separate bank.


If you do add a separate bank, I would first figure out exactly how much you need. How many amp hours does your pilothouse panel use overnight? Size the new bank for that load. You then could take that current set of cables that run to the pilothouse panel and use those with your charger to charge the PH bank. Many chargers are setup to be able to charge multiple banks so your charger could charge both the house bank and Pilothouse bank. The downside to that is that the PH bank would only be charged while you are either plugged in or have the genset running.


Alternatively, use the cables to the PH panel and use an ACR to combine the house and PH banks while they house bank is getting charged. This has the advantage of charging the PH bank regardless of the charging source, such as your engine alternator. The down side is that the two banks should have the same charge profiles.


Another option is to use a DC->DC charger using the existing cables to the PH to charge the PH bank from the house bank. This has the same advantage as the ACR in that they PH bank would be charged whenever their is a charge source to the house.


All in all, I would likely opt for the ACR if you just can't expand your house bank and aren't willing to be a little less profligate with your electricity at night.

You can expand your current bank (which would be my approach too) without having the additional batteries physically right against the existing set.....which seems to be your concern in doing this. Find a convenient place elsewhere and cable together with appropriately sized cables. Surely you can find somewhere other than the pilothouse for another 2~4 gc batts?

Arthurc said:

...this is purely an issue of me greedily wanting to not worry about counting amps every night while leaving things like my full Nav and N2K network, and camera system running 24x7 since they do things like anchor watch. The tall batteries are an option but looks to be several thousand dollars based on what I looked at, more batteries arent really an option.
Also its not about solar as I generally kill my Genset about sun down, its purely a question of added capacity for the night.

The tall batteries might be the simplist but does mean in the case of water in the bilge I am out of luck. Although I haven’t actually tested operating the boat with the battery switch off.... (I have a separate starting system)

Click to expand...

Maybe describe how much water you might be worried about in that mid bilge?

(FWIW, our batts are in the engine room, but high enough so water in the bilge (rare) isn't an issue.... and if there's enough water to kill batteries, I'd have way more important problems to deal with -- like launching the tender, etc.)

I haven't priced tall batteries like L16s, and I don't see where you mentioned how many pairs of 6Vs you have in your 12V system -- but are they really that much more expensive than normal GC2s? -- and maybe you could recoup a bit of that cost if you can sell off your current batts afterwards, presumably in good shape?

Greed is at least more easily managed when clearly identified.

Maybe turn on your genset again just before bedtime, run it for (an hour?) to top up batts just before you retire?

How much of that stuff do you need to mount an anchor watch? Or for deptch alarms? For example, we have a couple different GPS units and a couple different sounders, but I don't really need to run both of each overnight for an anchor watch...

How does the camera system contribute?

Is your anchor light an LED?

-Chris

I would second that increasing the size of the existing house battery bank. if you have the height clearence you might consider replacing the existing 6v batts with l16s

I’ll take a look at the height options plus maybe look at extending the bank into the forward bilge which may have space. That all makes sense and would be simpler.

As for water a majority of my throughhulls are in that midship bilge and so a Jose issue might flood it while likely wouldn’t flood the engineroom much before I was able to close it. The starter batteries are mounted high in the eng room for both the main and Genset.

I have 3 48v banks. Each connected by a relay and a homemade voltage sensing system that switches to the next bank when the volts go below a set point. If all three are down, the inverter starts a generator. I can go 2+ days with 120v lights, reefer and freezer. I went to a 48v inverter because the needed cable sizes are smaller and I can put the banks some distance from the inverter.

Why do you need the cameras on all the time, or any of the equipment that is causing the draw down? I disagree about the AGS, having been an avid actual user of one rather than fearful speculator about them.

caltexflanc said:

Why do you need the cameras on all the time, or any of the equipment that is causing the draw down? I disagree about the AGS, having been an avid actual user of one rather than fearful speculator about them.

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I never said I needed any of this on but I do prefer not to hassle with it. The cameras record 24x7 which is great if anything ever happens in the anchorage, such as the rope that got pulled all around my deck a few months ago when I was at the dock, turns out it was a playful otter, irritating but good to know versus it being a human.
Secondly they are super handy for anchor watch or just in general, they go to any TV or ipad in the boat so its easy to flip the TV input and get a view of any changes in the anchorage. That’s the same reason I run my TZT12 plotter as the anchor alarm, it also displays to any TV in the boat, really quick and easy to see where you are.

I’m on full LEDs, new fridges, etc so Ive thought about efficiency of every device, but at this point I would rather spend additional money to not have to worry about every amp right now, priority is on making sure we are having fun and the kid is safe.

AC

Dyno L16 deep cycle batteries should cost about $350 a battery. The question is how many do you need. I run 8 of them. This gives me just shy of 1600 amp hours.

I believe I’m running 6, I thought they were significantly more when I looked at fisheries but may have been looking at the wrong ones.
When I go to the boat Friday I’m going to see if I can move to the L16s and add 2-4 more to the forward bilge (only a bulkhead between them)

Thanks for all the advice, love this forum.

Looks like the ones I was looking at were Lifeline brand, 650 a piece. Thoughts on a better or more cost effective brand?

Dyno makes only commercial grade lead acid batteries for both the fishing industry and the railroads. You won’t find a better lead acid battery. I would need to price check but I bet I can sell them to you for $350 a battery.

Arthurc said:

Looks like the ones I was looking at were Lifeline brand, 650 a piece. Thoughts on a better or more cost effective brand?

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Lifeline are AGMs. so they do come with some advantages... as for example, if servicing is difficult due to access, or if you need to mount them sideways or whatever. When I installed a bank of Lifeline 6V 4CTs (the regular GC2s) our local dealer agreed to match internet prices... so my net costs were much lower than MSRP. My previous Odyssey AGMs on that bank laster 11-12 seasons, so overall cost over their lifetime isn't necessarily out of line.

OTOH, if wet batteries work for you, I see lots of recommendations for Trojans, and some for East Penn/Deka.

-Chris

We had a similar conundrum on Delfin. Although we don't run anything at night other than an anchor light at night unless other electronics are needed for anchor watch during storm conditions, we would use around 300 amps @ 24 vdc per day at anchor. With a 1250 amp bank and the extended charge time to get lead acid ( in this case AGM) batteries back up to FULL charge I narrowed the solution down to either a quiet night time genset (settled on NextGen 5kw) that would run during the late pm to bedtime, or LiFePO4 batteries that would recharge very quickly using the existing genset.

Either would have given me what I wanted, which was peace and quiet while charging, or if I had to run the 20kw genset, a much shorter run time. I settled on the LiFePO4 solution and am quite happy with it. While it doesn't solve your current time restricted need for a solution, you should think through how much power you need over how long a period of time, and either be prepared to run a big genset a whole lot, or think through a quieter, more efficient solution.

FWIW, running your existing batteries to 11.5 volts will kill them off pretty quickly. That is about 80% discharge and you won't get more than a couple hundred cycles out of lead acid batteries, using (abusing) them that way. If it were me, I wouldn't just add more capacity of a system I doubt you'll like over the long haul. I'd take the trip and reduce the load so the batteries don't ever drop below 12 volts, then take out the checkbook and install a night generator if you want to stay with LA batteries, or put in a bank of Lithium that are just fine being discharged 75% - 80% and will still give you thousands of cycles. I found the cost to be about the same either way.

ranger42c said:

Lifeline are AGMs. so they do come with some advantages... as for example, if servicing is difficult due to access, or if you need to mount them sideways or whatever. When I installed a bank of Lifeline 6V 4CTs (the regular GC2s) our local dealer agreed to match internet prices... so my net costs were much lower than MSRP. My previous Odyssey AGMs on that bank laster 11-12 seasons, so overall cost over their lifetime isn't necessarily out of line.

OTOH, if wet batteries work for you, I see lots of recommendations for Trojans, and some for East Penn/Deka.

-Chris

Click to expand...

Chris, the OP might benefit from hearing what capacity you drew your AGMs down to before fully re-charging that allowed you to get so many seasons. I got the same out of my AGMs and I never let them get below around 35% discharged.

Delfin said:

Chris, the OP might benefit from hearing what capacity you drew your AGMs down to before fully re-charging that allowed you to get so many seasons. I got the same out of my AGMs and I never let them get below around 35% discharged.

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Good point.

We almost always started recharging at least when one or the other of our main banks got down to 50% SOC as estimated from a simple voltage reading. That doesn't mean we always (or even often) drew them down to 50%, though... that was just a lower limit we always tried to respect.

A very few times, 2 or 3 maybe, we drew that bank down to where I had to use my parallel switch to restart our starboard engine. These are dual purpose start/half-of-house banks; those instances were as we were trolling for extended periods on the opposite engine (i.e., with the starboard engine off)... and with all our bridge electronics running from that starboard bank.

And then our normal regime at anchor is twice/day using the genset and charger, coinciding with cooking times and making hot water, etc... no matter what the battery SOC was. We rarely anchor for more than a week or two at a time.

And then we'd usually be back at the dock, shore power, etc.

-Chris

"We almost always started recharging at least when one or the other of our main banks got down to 50% SOC as estimated from a simple voltage reading."

This is very difficult as for voltage to be used as a measure the batt has to be out of the system for may hours.

A SOC meter will be far more accurate. About $150 + install.

FF said:

"We almost always started recharging at least when one or the other of our main banks got down to 50% SOC as estimated from a simple voltage reading."

This is very difficult as for voltage to be used as a measure the batt has to be out of the system for may hours.

A SOC meter will be far more accurate. About $150 + install.

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Yeah, sure... but it was close enough for our purposes. I haven't felt like I need all that much better accuracy...

Especially after reading about all the work it takes to calibrate most SOC meters... and to keep them calibrated over the life of a battery bank...

-Chris

Thanks for the advice everyone, I’m going to go with upgraded L16 AGM (400ah at 6v) batteries which should boost my amp hours to 1200, will see how that does for the summer trip. I did find a place to put 2 more so going to 1600ah wouldn’t be super hard.

Will re-evaluate this fall. Appreciate the advice, super helpful (as always).

ranger42c said:

Yeah, sure... but it was close enough for our purposes. I haven't felt like I need all that much better accuracy...



Especially after reading about all the work it takes to calibrate most SOC meters... and to keep them calibrated over the life of a battery bank...



-Chris

Click to expand...

Second time I have link this article that CMS wrote. Balmar Smart Gauge is very easy to install, self calibrating, and sounds perfect for an simpleton such as myself.

https://marinehowto.com/smart-gauge-battery-monitoring-unit/

dhays said:

Second time I have link this article that CMS wrote. Balmar Smart Gauge is very easy to install, self calibrating, and sounds perfect for an simpleton such as myself.

https://marinehowto.com/smart-gauge-battery-monitoring-unit/

Click to expand...

Thanks. Yep, I've read those... along with the bazillions of posts on CF about calibrating this, that, and the other monitoring system. Just seems to be too much work for too little gain, to me. (And BTW, several of the posts on CF about the Smart Gauge make that "self-calibrating" thing seem like a stretch...)

But I admit I do try not to be a slave to the boat, so when I can eliminate a chore (servicing batteries, for example) I'll often opt for that when my wallet thinks it's viable. Hence our AGMs, although in our case that was also driven by the extra amount of work would take to service ours due to access issues. And hence my not wanting to add something that will then require my attention.

Anyway, when it comes to batteries in general, I've taken the line of least resistance: add as much capacity as is easily possible, then work with what we've got as best we can.

But in general, because of our "cruising" style (such as it is) and because of our cooking/hot water systems, we've usually gotta run the genset a couple of times/day at anchor anyway... so installing and then yutzing around with a monitor to keep it accurate down to the last amp... really wouldn't change that behavior, anyway.

-Chris

"so installing and then yutzing around with a monitor to keep it accurate down to the last amp... really wouldn't change that behavior, anyway."


Worrying about the "last amp" is only worthwhile to be sure the batt set is up to 100% charged fairly often..


Bouncing between 40%-50% full and 85-90% full is what most cruisers do as that last 10% takes noise making "forever" or the dock, or solar.


Going much below the usual 50% and NOT getting to 100% fairly often is what harms batts.


The usual cure is to oversize the set so as the loss accumulates there is still enough left for a good std of living.

ranger42c said:

But in general, because of our "cruising" style (such as it is) and because of our cooking/hot water systems, we've usually gotta run the genset a couple of times/day at anchor anyway... so installing and then yutzing around with a monitor to keep it accurate down to the last amp... really wouldn't change that behavior, anyway.

Click to expand...

I get what you are saying. There are some things that I enjoy messing around with and other stuff that I’d just rather not do (washing and waxing for example).

So often folks on forums (like me) can get lost in the minutiae. Yes, a coulomb counter should be properly setup and it should be properly synchronized with the battery bank and the setup should be adjusted each year to account for the loss of the bank capacity. Some would suggest doing a load test to find out exactly what the Ah capacity of the bank is so that you can properly setup the amp counter. I’m not smart or patient enough to do all that.

That is why the idea of the Smart Gauge appeals to me. It will tell me what the SOC is on the bank while it is being discharged. If want to keep the state of charge of my bank over 70%, I can use it to help me do that. Of course, I don’t know anything, but I do trust a professional that does. This is just a cut from the article I referenced before by Rod Collins’ (CMS or MaineSail) on his website.

“The difference is the Smart Gauge does this quite accurately and tracks SOC regardless of temperature, battery age etc.. The longer you use the Smart Gauge, and leave it connected to the bank, the more accurate it becomes.”

No one needs to use a battery monitor. OTOH, with a simple tool like this, I don’t think anyone should feel it would be a hassle to use. The only reason I have not installed one yet is that I’m kind of lazy. I also am still trying to find a good location to mount it in my boat. I think I am going to try and come up with a box so i can do a surface mount rather than cutting a large hole in my teak somewhere.

dhays said:

I get what you are saying. There are some things that I enjoy messing around with and other stuff that I’d just rather not do (washing and waxing for example).

So often folks on forums (like me) can get lost in the minutiae. Yes, a coulomb counter should be properly setup and it should be properly synchronized with the battery bank and the setup should be adjusted each year to account for the loss of the bank capacity. Some would suggest doing a load test to find out exactly what the Ah capacity of the bank is so that you can properly setup the amp counter. I’m not smart or patient enough to do all that.

That is why the idea of the Smart Gauge appeals to me. It will tell me what the SOC is on the bank while it is being discharged. If want to keep the state of charge of my bank over 70%, I can use it to help me do that. Of course, I don’t know anything, but I do trust a professional that does. This is just a cut from the article I referenced before by Rod Collins’ (CMS or MaineSail) on his website.

“The difference is the Smart Gauge does this quite accurately and tracks SOC regardless of temperature, battery age etc.. The longer you use the Smart Gauge, and leave it connected to the bank, the more accurate it becomes.”

No one needs to use a battery monitor. OTOH, with a simple tool like this, I don’t think anyone should feel it would be a hassle to use. The only reason I have not installed one yet is that I’m kind of lazy. I also am still trying to find a good location to mount it in my boat. I think I am going to try and come up with a box so i can do a surface mount rather than cutting a large hole in my teak somewhere.

Click to expand...

I can't use a Smart Gauge on Li batteries, but was surprised at how accurately the old Link 2000 is. Shows me how many amps have been taken out, and I know it is accurate because if I let the charge source continue to pump current to the batteries after the acceptance rate drops quickly from 200 amps to 20, the voltage starts going up fast, which is the expected behavior for this battery chemistry when it is full.

The Link 2000 is a piece of cake to install..

Turns 8 camera NVR off and goes back to bed.
Reality is it probably doesn't use much but it still uses.